Učënye Zapiski Kazanskogo Universiteta. Seriâ Estestvennye Nauki (Mar 2017)
The Study of Natural Isolates of Fusarium spp. Micromycetes – Ligninolytic Enzymes Producers
Abstract
It is known that many basidiomycetes, white rot agents of wood in particular, produce ligninolytic complex enzymes, the most important of which are laccase, manganese peroxidase, and lignin peroxidase. Using these basidiomycete enzymes, promising methods have been developed for disposal of logging and plant farming wastes, paper stock delignification, cloth bio-bleaching, and production of wooden fibreboards; however, these techniques are not commonly applied on an industrial scale. It should be noted that wood lignin can be also destructed by various micromycetes, such as Fusarium, Trichoderma, Aspergillus, Penicillium, etc. Nevertheless, the range of ligninolytic complex enzymes produced by them, as well as the level of their activity and localization in a cell, have been studied insufficiently. Thus, it is not possible to fully appreciate the ligninolytic potential of micromycetes. The purpose of this research is to evaluate the ability of natural isolates of Fusarium spp. to produce laccase, manganese peroxidase, and lignin peroxidase. Furthermore, the level of activity of these enzymes in the culture liquid and cell mass of producers has been determined. The following natural isolates of micromycetes have been isolated and identified from natural envi-ronments of the Kirov region: F. culmorum, strain 3, F. sporotrichioides, strain 12, and F. solani, strain 52, all capable of degradation of wood lignin and carrying simultaneously genetic determinants of all the three major ligninolytic enzymes – laccase, manganese peroxidase, and lignin peroxidase. We have studied the dynamics of the activity of these enzymes in the culture liquid supernatants at deep micromycete cultivation. The enzyme activity has been determined by the spectrophotometric method. In terms of laccase and manganese peroxidase production, two micromycete strains – F. culmorum 3 and F. sporotrichioides 12 – have been almost as good as the basidiomycete T. versicolor. According to lignin peroxidase production under the same conditions of cultivation, F. sporotrichioides 12 has been 2.7 times better than T. versicolor. Regarding the ability to accumulate biomass in case of deep cultivation on rich and synthetical media, Fusarium has turned out to be 1.5–1.7 times better than T. versicolor. All micromy-cetes have been shown to secrete laccase, manganese peroxidase, and lignin peroxidase into the culture medium; the enzyme output in culture liquid has been up to 75.5–91.9%. Therefore, it has been demon-strated that Fusarium micromycetes are promising producers of ligninolytic enzymes, further investigation of their biotechnological potential is needed.
